We have postulated that oxidative stress may be important in the development of retinopathy, and have collected (1) metabolic evidence in the retina of diabetic rats that is consistent with increased oxidative stress (supranormal thiobarbituric acid reactive substances and subnormal glutathione [GSH], and (2) histologic evidence that antioxidant supplementation inhibits the development of lesions of the retinopathy. Since "antioxidants" can act also be mechanisms not related to oxidative stress, and since some investigators recently have questioned whether diabetes results in an oxidative stress at all, we will further explore the relationship of oxidative stress to diabetic retinopathy in 3 specific aims: Firs, we will evaluate retinas from normal and diabetic humans and animals, determining the amount and distribution of specific chemical modifications that are known markers of oxidative stress. In this way, we can provide perspective on the nature and degree of oxidative that the retina is exposed to in diabetes. Second, we will investigate the relationship between oxidative stress and accelerated death of retinal cells in diabetes, using 3 different but pertinent animal models (1) experimentally diabetic rats fed supplemental antioxidants, (2) diabetic mice over-expressing the anti-oxidant enzyme, MnSOD, and (3) diabetic mice deficient in caspase-1 (an enzyme which is related to oxidative stress and which our data suggests may be pro-mice deficient in caspase-1 (an enzyme which is related to oxidative stress and which our data suggests may be pro-apoptotic in diabetes). Third, we will investigate the possibility that a recently reported beneficial effect of nerve growth factor (NGF) on the development of retinopathy in diabetic rats is mediated largely via effects on the neurotrophin on diabetes-induced oxidative stress in the retina. Other investigators have failed to find receptors for NGF on vascular endothelial cells, suggesting the very interested conclusions which, if substantia, suggests that NGF on vascular endothelial cells, suggesting the very interesting conclusion which, if substantiated, suggests that the beneficial effect of NGF on retinopathy is mediated directly on the vasculature as expected, but instead via some other nearby cell type such as retinal neurons or glial cells. Each of the three specific aims proposed focus on the role of oxidative stress in diabetic retinopathy, and are expected to provide new insight into the pathogenesis and treatment of the retinopathy.